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Car Audio Do you live in your car? Then you need to be able to listen to some high-quality music.
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Old 01-28-2005, 08:59 PM   #1
Diceman83
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Box shape

OK, I've read just about every thread dealing with boxes, sealed vs ported, bandpass, etc. For my listening tastes, I think I've decided on a sealed enclosure, mainly because I prefer SQ over loudness. I know, it's a little different than most people, but that's me.

However, I've only seen a little bit comparing cubic shaped vs tubed enclosures, and I was curious about the advantages and disadvantages of each. I was also wondering about hybrid designs, with say, a smallish cube just big enough for the sub with a big PVC pipe embedded in it to bring up the total volume. Please don't flame me, I'm a beginner at this stuff, and I don't really know the do's and don'ts of this art. Also, what about 3D orientation? Does the sub have to point directly back or can it be pointing up or sideways? I know forward is bad, so that direction is out. Ideally I'd like to take some of the space in the back behind one of the wheel wells so I can still use most of my trunk.

I'd like to build something interesting to look at that sounds good from the frequencies of like 20 Hz to like 200 Hz (or where ever the midrange speakers start to take over). I don't really want to go totally loud like most of you guys do (no offense), so sound quality over the whole range at lower volume levels (like less than 100 dB) is what's important to me. I have some nice 3/8" lexan I'm planning to make at least one side out of, for a window with some lights .

As far as what I have to work with: I got a decent deal on a used Rockford Fosgate 15" hx2 sub (with the 4 ohm dual VC's) and a Soundstorm F500.2 amp. I know these aren't the best stuff out there, but it's what I can afford. Being able to get like 400 Watts out of $160 isn't too bad I would think. I have a '93 Honda Accord EX sedan, with a good Panasonic head unit and some pioneer coax mids.

Sorry this is so long, but these are the questions I have after reading for like 3 days.

Summarized:
  • speaker box: square vs tube (hybrid?)
  • cone orientation: straight back vs up, sideways, etc
  • frequency range?
Thanks guys!
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Old 01-28-2005, 09:37 PM   #2
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Re: Box shape

not an expert just giving my 2 cents..

as far as i knwo there is really no difference between round enclosures and square ones. I would think that the only thing that matters is volume. shape probably doenst have an effect. most people build boxes because theyre easy. therefore, i doubt a hybrid would even do anything except take up volume in your box. i would suggest just an MDF box. or a fiberglass box if you cant get one done.

as far as where to point your subs.. it depends on your car. i wouldnt suggest firing them to the side. ive heard a car liek this and it wasnt good. most people fire them back, but you might want to try flipping a box around back there and seeing what sounds best.

and the frequencies.. yeah youll need sealed to get the range you want. hoewver you wont get good responce from your sub at 200 hz trust me. most people have their mids take over at like 60-90 hz.(i think) mine are at like 80. how good are those infinities? i doubt your midbass will be very strong, but id say 80-90 hz would be good.

the sub is ok, but more meant for getting loud. actually from what i remember this sub had very poor sound quality, but youll figure that out after you get it in your car and listen to it for a while.

is your amp a 2 channel? im assuming its only stable down to 4 ohms bridged.. problem there being you cant wire your sub for 4 ohms. you would haver to wire it to 8 ohms and then youd really only be getting like 200 watts to your sub. dont knwo the specs on either sub or amp but may want to look into this.

if you end up haveing to get rid of one or the other, ditch the sub and check out an atlas 15 from ascendant audio (www.ascendantaudio.com) BUT.. get back with us first about whether that amp will work with the sub.
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Old 01-28-2005, 10:10 PM   #3
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Re: Box shape

ok, the sub is rated as follows:

Frequency Range: 24-200 Hz
Dual 4 ohm voice coils rated to 300 Watts each
Q factor: 0.53 Qts (quarts?)
Recommended Box volume: 2 - 5.5 ft^3



amp specs:

Input level adjustment
Line level & speaker inputs
Freq resp (+/- 3 dB): 9 Hz - 50 kHz
Variable low pass crossover: 40 Hz - 150 Hz
High pass crossover
THD @ RMS output: .01%
Variable Bass Boost: 0 - +18dB
S/N ratio: 103 dB
Channel separation: 90 dB
Power MAX 2W 500W x 2
Power RMS 4W 200W x 2
Bridged Power 1000W x 1
Damping Factor 125+

I was thinking about hooking the connections up in parallel so it's a 2 Ohm woofer and just using a single channel on the amp. That way it's using 500 watts of the rated 600 watts, which is close enough for me. I could also use both channels in 4 ohm mode for a total of 400 watts. I guess either way would work.

It's going to be a few months before I can actually install and test this, because it's so freakin cold outside. (it's -5 degrees F at the moment) I would like to build the box anyway, and maybe if there's a mid winter thaw, I could install it then. Luck favors the prepared, I guess.

Anyone have a response to "box shape doesn't matter as much as total volume enclosed"?
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Old 01-28-2005, 10:56 PM   #4
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Re: Box shape

do you already have the equipment? I would suggest different things for a sq setup.
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Old 01-28-2005, 11:20 PM   #5
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Re: Box shape

I know there are tons better things out there, I'd just like to get the best sound possible from 160 bucks worth of stuff. I do already have the equipment, and I doubt I'll be upgrading anytime soon. I'm gonna have some fun making the sub enclosure though, so it isn't all bad. I figure if I can design something that makes a crappy setup sound pretty good, I'll have learned enough by the time I have the money to get a really nice setup, I'll be in good shape to make that sound incredible.

For the moment I'm wondering if it's just volume of the sealed enclosure that matters or if it has to be a generally regular shape (cube, tube, sphere, etc).
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Old 01-29-2005, 04:02 AM   #6
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You won't get any SQ worth worrying over the box with that sub. As for your assumption about a lot of us choosing SPL over SQ, it's quite the opposite here.

As for the box, most people make a rectangular or cubed box, but I think usually rectangular. No weird shapes or designs. It becomes difficult to measure the proper volume inside the box and makes sound travel weird in it (this is just stuff that sounds right to me, some of it I'm sure of, but the shape thing with the sound travel I'm not). Take my advice with a grain of salt, a large one.
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Old 01-29-2005, 09:34 AM   #7
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shape doesn't matter in a box, only volume. The problem in making odd shapes is figuring out the volume and making it rigid (so it won't flex)
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Old 01-29-2005, 09:10 PM   #8
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Re: Box shape

perfect cubes are the absolute worst sound producers. The golden ratio is optimal. 1W*0.618D*1.1618H or at least that is what the myths say.
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Old 01-29-2005, 11:53 PM   #9
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Re: Box shape

Make a triangular box.
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Old 01-30-2005, 12:48 AM   #10
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ummm ... if it were a triangle, it wouldn't really be a "box" ..... but it would be an interesting looking enclosure Sometimes a cube can have standing waves, they are generally avoided
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Old 01-30-2005, 03:43 AM   #11
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Re: Box shape

So I was 50% accurate with my post, I'm catching on and learning .
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Old 01-30-2005, 07:49 AM   #12
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Re: Box shape

has anyone used PVC pipe in any part of their boxes before? I know it's not a usual material, but I don't like to do things the standard way. A little variaty and experimentation never hurt anyone . Because of space issues I was thinking about using some 6" diameter thick walled PVC as extensions through unused parts of my trunk. I've done a bunch of calculations, taking the thickness of 3/4" MDF and the sub, and the approximate volume of my design is 4.5 cubic feet, which is near the upper limit of the sub's sealed enclosure rating. I can add some stuffing to simulate a larger volume too. I'll work on some sketches with a picture of my trunk and post it later today. You're probably going to think I'm nuts, but like I said, I like to experiment.
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Old 01-30-2005, 07:59 AM   #13
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Re: Box shape

you have no idea. we used 6" Irrigation PVC to make a TL for one of thoes old audiobahn 6" woofers. Probably some of the best SQ i have heard from audiobahn. and we had good responce down to 30Hz (40Hz tuning). and we used some of their sweeping elbow's to make the curves. it worked out nice. he used 0.87kg of acoustic whool stuffing (i didnt do the calcuations, dont ask me about stuffing to change tuning, i know alot for such a youngin' but not that much) to lower the tuning frequincy and it turned out only needing like 7ft of line length.
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Old 01-30-2005, 05:43 PM   #14
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a 6" subwoofer ? ............... the only problem with pvc is it's not to strong and may flex with more powerful subs.
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Old 01-30-2005, 08:17 PM   #15
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Re: Box shape

That's what's nice about tubes... a little bracing is really easy. Just crank a couple of large hose clamps on it and it won't flex much. I'm getting pretty close to a final design, after carefully measuring the inside of my trunk. I don't think I'll have any pics tonight though, sorry. I was fighting with a friend's computer all afternoon.
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